Population Genetics Overview (Exam 3)

Population

• A population refers to individuals of the same species inhabiting the same geographical area at a specific time, with the potential to interbreed.

Mutation

• A permanent alteration in an organism's DNA sequence.
• Mutations occur randomly and are the primary source of new alleles.
• Only mutations affecting reproductive cells are passed down to offspring.
• Mutations can be beneficial (positive) or detrimental (negative) to an organism's fitness.
• Deleterious mutations are often removed by purifying selection, reducing their frequency.

Gene Flow

• The movement of alleles between different populations.
• Gene flow is a random process with respect to fitness.
• Occurs through migration of individuals.
• Can reduce genetic differences between populations.

Genetic Drift

• A random fluctuation in allele frequencies within a population.
• Often occurs due to random mating and death patterns.
• It is a random process with respect to fitness.
• Most prominent in smaller populations.
• Can lead to the loss of alleles.

Natural Selection

• Non-random process favoring individuals with heritable traits that increase survival and reproduction.
• The only mechanism consistently contributing to adaptation within a population.
• Influenced by selective pressures, such as environmental conditions (temperature, rainfall) and interactions with prey or predators.
• Biological fitness refers to an individual's ability to produce viable offspring relative to others in the population.
• Adaptation is a heritable trait enhancing an organism's fitness in a specific environment.
• Artificial Selection is the intentional breeding of plants or animals for desired traits, often driven by human intervention.

Sexual Selection

• A form of natural selection where individuals of one sex choose mates based on specific traits or behaviors.
• Typically driven by female choice where males compete for mates.
• Can lead to sexual dimorphism, where males and females of the same species display distinct physical characteristics.

Evolutionary Arms Race

• A continuous cycle of adaptations between predator and prey species.
• As one species evolves, the other responds with counter-adaptations, resulting in ongoing coevolution.

Coevolution

• The reciprocal evolutionary influence between two species.
• Occurs in predator-prey interactions, competitive species, and mutualistic relationships like pollinators and plants.

Microevolution

• Small-scale evolutionary changes within a population resulting from allele frequency shifts.

Macroevolution

• Large-scale evolutionary changes occurring over long periods (geologic time), leading to the formation of new species (speciation).

Speciation

• The process of forming a new species through evolutionary mechanisms.

Adaptive Radiation

• Rapid diversification of organisms, particularly when exposed to new environments with diverse challenges, resources, and ecological niches.
• Often observed after mass extinction events or in isolated archipelagos (e.g., Galapagos finches).

Biotic Interchange

• The breakdown of barriers between previously separated biotas, leading to significant biodiversity changes.
• An example is the Great American Biotic Interchange, where the Isthmus of Panama connected North and South America, allowing the exchange of species.

Sympatric Speciation

• The formation of new species without geographic separation.
• Driven by ecological niche differentiation or polyploidy, resulting in reproductive isolation within a single population.

Evolutionary Novelties

• Complex structures arise from gradual modifications to existing structures over evolutionary time.

Evolutionary Trends

• Evolution is not goal-oriented.
• The interaction between organisms and their environment drives evolution, not the desire for specific traits.

Taxonomy

• The scientific classification of organisms based on hierarchical categories.

Phylogeny

• The evolution of a group of organisms.

Phylogenetic Trees

• Visual representations of evolutionary relationships among organisms.

Synapomorphy

• A shared, derived characteristic used to support evolutionary relationships between taxa.

Ancestral Trait

• A trait that existed in an ancestor

Derived Trait

• A trait that is a modified form of an ancestral trait

This quiz covers essential concepts in population genetics, including definitions and implications of population, mutation, gene flow, and genetic drift. Explore how these factors influence the genetic makeup and evolution of species. Test your understanding of how allele frequencies change over time in populations.